Process for preparing methyl- and ethyl-substituted primary anilines

ABSTRACT

A process is disclosed for the preparation of methyl- and ethyl-substituted anilines by contacting anilines of specified formula at about 250°-525° C. and about 10 kPa-10 MPa of pressure in the of presence of a nonbasic metal oxide catalyst which when it is a zeolite has pore dimensions of at least about 0.52 nm and has cages with dimensions greater than about 0.75 nm.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a division of application Ser. No. 559,184, filedDec. 7, 1983, now abandoned.

BACKGROUND OF THE INVENTION

This invention relates to a process for the preparation of methyl- andethyl-substituted anilines.

Methyl-substituted anilines are useful in a variety of applications suchas in the preparation of dyes, herbicides, insecticides, plant growthagents and antiknock agents for gasoline engines. The anilines aregenerally prepared by nitration of the appropriate methyl benzenefollowed by reduction of the resulting nitro compound. This processdepends upon the availability of the appropriate nitro compound which insome instances is unavailable or available only in limited quantities.For example, m-toluidine is important as an intermediate in dyes andagricultural chemicals. However, in the foregoing nitration-reductionprocess, only 4% of the toluidines produced are m-toluidine. As aresult, separation of m-toluidine is a complex process and consequentlythe meta-isomer is the most expensive of the toluidines.

U.S. Pat. No. 3,868,420, issued to Evans et al. on Feb. 25, 1975,discloses a process for producing phenylamines alkylated in the orthoand/or para positions by alkyl groups of 1-4 carbon atoms andunsubstituted on the amino group which comprises reacting a suitablephenylamine with an alkanol of 1-4 carbon atoms in the vapor phase at atemperature of from 350° to 450° C. in the presence of an aluminum oxidecatalyst or an aluminum oxide/molybdenum oxide mixed catalyst, saidcatalyst having a minimum surface area of 50 m² /g. U.S. Pat. No.3,931,298, issued to Wollensak on Jan. 6, 1976, discloses a process forconverting hydroxy-substituted aromatic compounds to the correspondingamine by reacting the aromatic hydroxy compound with ammonia in thepresence of a catalytic amount of a cyclohexane and in contact with ahydrogen-transfer catalyst, most preferably palladium. U.S. Pat. No.3,960,962, issued to Shubkin on June 1, 1976, discloses a similarprocess wherein the catalyst comprises metallic palladium bonded to aphosphinated polystyrene resin.

U.S. Pat. No. 4,188,341, issued to Fischer on Feb. 12, 1980, discloses aprocess for making 2,6-dimethylaniline or an N-substituted2,6-dimethylaniline comprising reacting an enamine of a specifiedformula at a temperature of between -30° C. and 150° C. with acrolein inthe presence of an inert aprotic solvent and heating the resultingreaction product to a temperature of between 100° and 400° C. in thepresence of a hydrogen-transfer catalyst and an amine of the formulaRNH₂ wherein R is --H or a specified lower alkyl.

Japanese Patent Application Publication Kokai No. 53-28128 discloses aprocess for para-methylation of anilines comprising reacting an anilinehaving para-hydrogens with methanol in the presence of an alkali metalsynthetic zeolite catalyst, particularly NaY zeolite. Preparation of2,4-dimethylaniline from o-toluidine and the preparation of p-toluidinefrom aniline are specifically disclosed.

T. Matsumoto, Chemistry Letters, p. 939 (1977), discloses theortho-methylation of 2,3-dimethylaniline with methanol over varioussolid catalysts with 5 wt % Ag on Al₂ O₃ showing the highest selectivityto ortho-methylation, that is, the production of 2,3,6-trimethylaniline.M. Inoue and S. Enomoto, Sekiyu Gakkaishi, 15, 372 (1972) studied themethylation of aromatic compounds with methanol in vapor or liquid phaseon various catalysts and specifically report the ortho-methylation ofaniline with methanol using 10% MgO/Al₂ O₃ catalyst to produceo-toluidine.

Japanese Patent Publication 28129/1978 discloses demethylation ofpolymethylanilines, which contain at least more than two methyl groups,in the presence of a catalyst composition of the formula A_(a) B_(b)C_(c) O_(d) wherein A is titanium; B represents more than one kind ofelement selected from zinc, zirconium and magnesium; C represents morethan one kind of element, selected from vanadium, chromium, manganese,tin, iron, cobalt, nickel, copper, molybdenum, tungsten, barium,calcium; O is oxygen; a is 1, b is 0.05 to about 20, and c is 0 to 1.0.Reaction temperatures of 440°-600° C. are disclosed. Ti--Zr catalystsystems are stated to give mainly p-demethylated products, such as2,6-xylidine from mesidine. Ti--Zn or Mg catalyst systems give o- and/orp-demethylated products, such as m-toluidine from 2,3-, 3,4-, and2,5-dimethylaniline, 2,4,5-trimethylaniline; and2,3,4,6-tetramethylaniline.

Japanese Patent Publication No. 1974-[Showa -49], 29,178 discloses aprocess for the synthesis of toluidines rich in m-toluidine bydealkylation of xylidines having a methyl group in a meta position at400°-700° C. in the presence of a dealkylation catalyst such assilica-alumina, alumina, silica, silica-magnesia and magnesia. Matsumotoet al., Chemistry Letters, pp 435-438 (1978) disclose a process forpreparing m-toluidine by hydrocracking 2,3-xylidine over metaloxide-supported nickel catalysts. The authors disclose that theselectivity of m-toluidine is influenced by side reactions, such asisomerization, and that the extent of isomerization can be related tothe acidic character of the metal oxide carriers.

SUMMARY OF THE INVENTION

The present invention provides a process for preparing one or moresubstituted anilines of the formula ##STR1## wherein R is --CH₃ or --C₂H₅ and n is 1 or 2 comprising contacting an aniline of the formula##STR2## with an aniline of the formula ##STR3## wherein R₁ and R₂ areboth methyl or ethyl, n₁ and n₂ are different and are individually aninteger from 0 to 3, and n₁ +n₂ is an integer from 1 to 5, saidcontacting being performed in the presence of a nonbasic metal oxidecatalyst at a temperature of from about 250° to about 525° C. and at apressure of from about 10 kPa to about 10 MPa, the formula I productbeing different from the formulae II and III starting materials and thetotal number of R groups attached to the resulting products being equalto the total number of R groups attached to the starting aniline; withthe proviso that when the nonbasic metal oxide catalyst is a zeolite ithas pore dimensions of at least about 0.52 nm and has cages withdimensions greater than about 0.75 nm.

BRIEF DESCRIPTION OF THE DRAWING

The FIGURE shows the kinetic paths followed by m- and p-toluidines inthe presence of aniline to reach equilibrium when equilibration takesplace over HY zeolite.

DETAILED DESCRIPTION OF THE INVENTION

Transmethylation is represented by the reaction ##STR4## where n₁, n₂,n₃, and n₄ represent the number of methyl groups on each aniline and n₁+n₂ is an integer from 1 to 5 with the proviso that n₁ and n₂ aredifferent and are individually an integer from 0 to 3 and n₁ +n₂ equalsn₃ +n₄. The product can contain one or more isomers corresponding to agiven number of methyl groups.

Transethylation proceeds in a similar manner.

The process of the invention includes

(a) the production of toluidine and dimethylaniline from aniline and2,4,6-trimethylaniline:

(b) the production of dimethylanilines from toluidine and2,4,6-trimethylaniline:

(c) the production of toluidines from dimethylanilines and aniline: and

(d) the production of isomers of a dimethylaniline and of a toluidine.

Catalysts suitable for the present process include molecular sieves,i.e., type X and Y zeolites, silica, alumina, silica-aluminacompositions, titania, zirconia, iron oxide, zinc oxide and Group V andVI metal oxides. Molecular sieves are commercially available as are manyof the other suitable catalysts. Metal oxide catalyst compositions foruse as catalysts in the present invention can be prepared byimpregnating a substrate with a solution(s) containing the desiredoxide(s), coprecipitating the desired materials on the substrate or byevaporation or spattering techniques well known in the art. When thecatalyst is other than a molecular sieve it is preferably amorphous.

When the nonbasic metal oxide is a zeolite (molecular sieve) it has poredimensions of at least about 0.52 nm and has cages with dimensionsgreater than about 0.75 nm. One skilled in the art will recognize thatas the number of methyl or ethyl groups on the reactants increases, theminimum pore and cage dimensions must increase correspondingly. Thezeolites X and Y are suitable in general for the transalkylation processof the invention. As used herein pore dimensions mean the aperturedimensions determined from crystal structure analyses, i.e., thecrystallographic free diameters of the channels as discussed by W. M.Meier and D. H. Olson, "Atlas of Zeolite Structure Types", published bythe Structure Commision of the International Zeolite Associations, 1978.The free diameter values are based on the atomic conditions of the typespecies in the hydrated state and an oxygen radius of 1.35 Å (0.135 nm).

In the process of the invention, the total number of methyl or ethylgroups on the primary anilines is substantially conserved. Minorportions of one or more reactants may undergo reactions in which some ofthe methyl or ethyl groups are lost by the anilines. However, except atthe highest temperatures, the major portions of the reactants undergothe foregoing transalkylation reaction in which the number of methyl orethyl groups on the reactant anilines equals the number on the productanilines.

The efficiency of a particular transalkylation is determined by the twosubstituted aniline reactants and the catalyst. The ease of the reactionincreases as the sum of n₁ +n₂ increases from one to five. Nonbasicoxides can catalyze the transalkylation of aniline and2,4,6-trimethylaniline (TMA). Acidic oxides, but not neutral ones,catalyze transalkylations where n₁ +n₂ =2 but strong acids, such as thehydrogen-exchanged Y zeolite (HY) and other silica-alumina compositions,are required when n₁ +n₂ =1. A discussion of acidic strengths iscontained in K. Tanabe, "Solid Acids and Bases". Academic Press, NewYork (1970).

A specific transmethylation is the reaction of aniline and2,4,6-trimethylaniline over a nonbasic metal oxide catalyst to produce2,4- and 2,6-dimethylaniline and o- and p-toluidine. The different metaloxide catalysts redistribute the methyl groups between2,4,6-trimethylaniline and aniline differently and can be groupedaccording to the selectivity they show toward producing either2,6-dimethylaniline and p-toluidine or 2,4-dimethylaniline ando-toluidine. In general, all four products are present to some degreeand, in addition, there may also be small amounts of m-toluidine andother dimethylanilines.

Silica-aluminas show high selectivity to 2,6-dimethylaniline andp-toluidine, that is, to the transfer of the methyl from thepara-position of 2,4,6-trimethylaniline to the para-position of aniline.The larger pore zeolites, such as zeolites X and Y, are examples of suchcatalysts, and the zeolite HY and the rare earth-exchanged X zeolite(REX) are especially preferred. Silica-alumina compositions includethose ranging from pure silica to pure alumina.

In contrast, supported titania, zirconia, iron oxide, zinc oxide, andGroup V and VI metal oxides show good selectivity to 2,4-dimethylanilineand o-toluidine, that is, to the transfer of the methyl from theortho-position of 2,4,6-trimethylaniline to the ortho-position ofaniline.

Each of these two groups of catalysts is more selective to theparticular dimethylaniline and toluidine at lower operating temperaturesand shorter contact times. In general, as the reaction conditions becomeincreasingly severe, by raising the temperature and/or increasing thecontact time, overall conversion is increased but selectivity to theparticular dimethylaniline and toluidine is reduced. The process of theinvention is conducted at a temperature of from about 250° to about 525°C., preferably from about 300° to 400° C., and at a pressure of fromabout 10 kPa (0.1 atmospheres) to about 10 MPa (100 atmospheres) for aperiod of time from about 0.1 sec to about 10 hours. The process of theinvention can be carried out in either a liquid or gas phase. Times ofabout 1 sec and 0.5 hr will often be suitable for vapor phase and liquidphase reactions, respectively. Preferably, a pressure of about 1atmosphere is used for vapor-phase reactions and autogenous pressure isused for liquid-phase reactions.

Some of the same metal oxides useful as a catalyst in the reaction ofaniline and 2,4,6-trimethylaniline are also useful as a catalyst in theother transmethylation processes of this invention and in particular forthe transmethylation represented by the reaction: ##STR5## where theproduct aniline with n₁ is a different isomer than the reactant anilinewith n₁ and the anilines with n₂ represent the same isomer. In essence,the aniline with (CH₃)_(n).sbsb.2 is a co-catalyst for the isomerizationof the aniline with (CH₃)_(n).sbsb.1 creating a transmethylation processwhich in effect results in the equilibration of one of the reactants.For these equilibration processes useful catalysts are determined by thesame rules concerning the sum of n₁ +n₂ as set forth earlier herein.

Equilibration of 2,4- and 2,6-dimethylaniline occurs when one or both ofthese isomers is reacted with either o-toluidine or2,4,6-trimethylaniline. The product can also contain some aniline, p-and m-toluidine and, when o-toluidine is a reactant,2,4,6-trimethylaniline. Equilibration of 2,3-, 2,5-, and3,4-dimethylanilines occurs when one or more of these isomers is reactedwith m-toluidine. The product can also contain small amounts of 2,4- and2,6-dimethylanilines.

Toluidine equilibration occurs when one or more toluidines are reactedwith aniline. The ortho and para isomers are rapidly interconverted andthe resulting two component equilibrium mix and the meta isomer thenslowly approach the three component equilibrium (17% p-, 31% o-, and 52%m-toluidine). This equilibration in the presence of HY zeolite catalystis the basis for the theoretical lines shown in the Figure. However,there are competing reactions. While a 10% solution of o-toluidine inaniline approximates the theoretical line shown in the Figure, a 1:1 mixof aniline and o-toluidine does not follow the curve, but bends towardthe three component equilibrium much earlier, and pure o-toluidineproceeds almost straight to the three component equilibrium. Thedisproportionation of two o-toluidines to a dimethylaniline and anilineappears to be competitive with the reaction of o-toluidine and anilineto give p-toluidine and aniline, but can be controlled by working withan excess of aniline. For equilibration the co-catalyst should bepresent in an amount sufficient to ensure that the equilibrationreaction dominates over reactions involving solely one of the reactants.

The invention is further illustrated by the following examples in whichall temperatures are in degrees Celsius and all percentages are byweight unless otherwise stated.

EXAMPLE 1

A solution of equimolar amounts of aniline and 2,4,6-trimethylanilinewas passed over 3 g of HY zeolite catalyst at atmospheric pressure and atemperature of 300°-400°, at a flow rate of 2 ml/hr with a nitrogen gasflow rate of 40 ml/min, in a 13 cm (5 inch) long - 1 cm (3/8 inch)diameter, heat resistant glass reactor heated with a split tube furnace.The HY zeolite used in this and later examples had a unit cell dimensionof 24.45 A, a SiO₂ /Al₂ O₃ ratio of 3.31, and a Na₂ O content of 0.15%.This process was continued for 30 minutes at a fixed reactiontemperature, e.g., 300°, and the resulting liquid effluent collected.The foregoing steps were then repeated at temperatures of 350° and 400°.Each resulting product was analyzed by gas chromatography using a 6.1 m(20 ft) by 0.32 cm (1/8 inch) stainless steel column packed withpolyethylene oxide of a molecular weight of about 20,000 and 1% KOH on80/100 mesh diatomaceous earth. Elution was carried out isothermally at200° with a nitrogen gas flow or 40 cc/minute. Retention times increasein the order aniline, ortho-, para- and meta-toluidine, 2,6- and2,4-dimethylaniline (DMA) and 2,4,6-trimethylaniline (TMA). The resultsare summarized in Table I. Selectivity to 2,6-dimethylaniline (2,6-DMA)is defined as the percentage of DMA product that is 2,6-DMA, i.e.,##EQU1## where the quantities of 2,6-DMA and 2,4-DMA are in moles. Theselectivity to p-toluidine is similarly defined as ##EQU2## Likewise,2,4,6-TMA conversion is defined as ##EQU3## The amount of m-toluidineand other DMA isomers in each product was negligible. As the reactiontemperature increased, the conversion of 2,4,6-TMA increased; however,selectivity to 2,6-DMA and to p-toluidine decreased.

EXAMPLES 2-11

Aniline and 2,4,6-TMA were reacted over other silica-alumina catalyststhat show high selectivity to 2,6-DMA and p-toluidine in a mannersimilar to that described in Example 1. The process conditions andresults are summarized in Table I. In each example, 3 g of catalyst wereused, reactor effluent obtained during the first 25 minutes of operationwas discarded, and product obtained during the next 5 minutes ofoperation was collected and analyzed using gas chromatography. A 3.0 m(10 foot)×0.32 cm (1/8 inch) stainless steel column packed with 2% UCON50 HB 5100 and 1.0% KOH on 80/100 mesh diatomaceous earth was used tocharacterize the product. A helium gas flow of 25 ml/min was used andelution was carried out at 150°. Elution of all peaks of interest tookplace within 14 minutes.

EXAMPLES 12-22

Aniline and 2,4,6-TMA were reacted over the titania, zirconia and otherGroup V and VI metal oxide catalysts which show good selectivity to2,4-DMA and o-toluidine in a manner similar to that described forExamples 2-11 and the process conditions and results are summarized inTable I. Note that a low selectivity to 2,6-DMA and p-toluidinerepresents a correspondingly high selectivity to 2,4-DMA ando-toluidine, respectively.

EXAMPLES 23-26

In order to demonstrate liquid phase reaction of aniline and 2,4,6-TMA,2 ml of an aniline-2,4,6-TMA solution and 0.5 g catalyst were placed ina shaker tube which was then evacuated at room temperature and sealed.The tube was heated to a desired reaction temperature, shaken for agiven time, and was then cooled to room temperature. The contents of thetube were analyzed by gas chromatography using a procedure similar tothat described in Examples 2-10. Process conditions are listed andresults summarized in Table II.

EXAMPLES 27-29

The use of nonbasic metal oxide catalysts to equilibrate anilines by atransmethylation process was demonstrated in a manner similar to thatused to demonstrate the transmethylation process described in Example 1.A solution of o-toluidine and 2,4- and/or 2,6-DMA was passed over 3 g ofHY zeolite catalyst at atmospheric pressure and a given reactiontemperature at a flow rate of 3 ml/hr with a nitrogen gas flow rate of10 ml/min in a vapor phase reactor similar to that used in Example 1.Liquid effluent was collected and analyzed by gas chromatography using aprocedure similar to that described in Examples 2-10. The processconditions used for each example and the results are summarized in TableIII. The product can contain aniline, p- and m-toluidine, and 2,4,6-TMAin addition to the 2,4- and 2,6-DMA and o-toluidine.

                                      TABLE I                                     __________________________________________________________________________                        Feed Ratio                                                                          Feed                                                                              N.sub.2                                                             Aniline:                                                                            Flow                                                                              Gas Reaction                                                                           Conversion                                                                          Selectivity                                                                         Selectivity                Example             2,4,6-TMA                                                                           Rate                                                                              Flow                                                                              Temp of    to    to                         No.  Catalyst       (moles)                                                                             ml/hr                                                                             ml/min                                                                            (degrees)                                                                          2,4,6-TMA                                                                           2,6-DMA                                                                             p-toluidine                __________________________________________________________________________     1   HY Zeolite     1     2   40  300  62    92    67                                                           350  77    58    46                                                           400  85    55    28                          2   91% Al.sub.2 O.sub.3 /6% SiO.sub.2                                                           1     3   10  375  15    79    88                                                           450  64    52    47                          3   10% Al.sub.2 O.sub.3 /SiO.sub.2                                                              2     3   10  375   8    82    100                                                          450  38    59    61                          4   12% Al.sub.2 O.sub.3 /86% SiO.sub.2                                                          2     3   10  300   6    92    100                                                          375  40    83    88                                                           450  81    57    53                          5   Attapulgus Clay                                                                              1     3   10  300   7    78    92                                                           375  17    66    81                                                           450  40    46    64                          6   Bentonite Clay 2     3   10  300  30    86    91                                                           375  29    71    82                                                           450  39    48    60                          7   Kaolinite Clay 2     3   10  450  15    50    65                          8   SiO.sub.2      1     3   10  450  17    47    63                          9   99% Al.sub.2 O.sub.3                                                                         1     3   10  375   3    50    75                                                           450  29    38    51                         10   HY Zeolite       3.5 3   10  260  51    92    76                                                   3   10  290  80    85    68                                                     1.5                                                                             25  260  68    87    78                                                     1.5                                                                             50  260  53    88    85                         11   REX Zeolite    1     2   40  300  59    83    Not                                                                           measured                                                     350  73    60                               12   TiO.sub.2      1     3   10  475  15     8    36                         13   ZrO.sub.2      1     3   10  375   2    43    50                                                           450  44    41    45                         14   10% ZnO/TiO.sub.2                                                                            1     3   10  450  17     8    30                         15   Sb/9Ti/O       1     3   10  375  19    21    25                                                           450  43    18    39                         16   10% MoO.sub.3 /Al.sub.2 O.sub.3                                                              2     3   10  375  14    25    39                                                           400  46    18    33                         17   19% Cr.sub.2 O.sub.3 /Al.sub.2 O.sub.3                                                       1     2   40  500  51    17    31                                             2     3   10  450  26    10    30                         18   24% ZnO/Al.sub.2 O.sub.3                                                                     2     3   10  450  10    20    50                         19   10% ZnO/10% Cr.sub.2 O.sub.3 /Al.sub.2 O.sub.3                                               2     3   10  375   4     0    50                                                           450  48    18    40                         20   10% WO.sub.3 /Al.sub.2 O.sub.3                                                               2     3   10  375  22    68    54                                                           450  56    38    52                         21   10% V.sub.2 O.sub.5 /Al.sub.2 O.sub.3                                                        2     3   10  375   8    14    31                                                           450  21     0    24                         22   20% Fe.sub.2 O.sub.3 /Al.sub.2 O.sub.3                                                       2     3   10  375   5     0    100                                                          450  17    26    48                         __________________________________________________________________________

                                      TABLE II                                    __________________________________________________________________________                    Feed Ratio                                                                    Aniline                                                                             Reaction                                                                           Reaction                                                                           Conversion                                                                          Selectivity                                                                         Selectivity                       Example         2,4,6-TMA                                                                           Temp Time of    to    to                                No.  Catalyst   (moles)                                                                             (degrees)                                                                          (hr) 2,4,6-TMA                                                                           2,6-DMA                                                                             p-Toluidine                       __________________________________________________________________________    23   HY Zeolite 2     350  2    71    94    76                                                      375  2    75    86    62                                                      350  4    69    91    75                                                      350  8    76    89    65                                                      375  1    70    88    71                                24   91% Al.sub.2 O.sub.3 /6% SiO.sub.2                                                       1     300  2    21    93    92                                     (Amorphous)                                                              25   87% SiO.sub.2 /13% Al.sub.2 O.sub.3                                                      1     300  2    12    93    100                                    Amorphous                                                                26   Sb/9Ti/O   2     350  2     6    42    33                                __________________________________________________________________________

                                      TABLE III                                   __________________________________________________________________________                                   Product                                                Feed Composition (mole %)                                                                     Reaction Temp                                                                         ##STR6##                                      Example No.                                                                          o-Toluidine                                                                         2,4-DMA                                                                            2,6-DMA                                                                            (degrees)                                                                             (mole percent)                                 __________________________________________________________________________    27     52.7  43.4 --   296     1                                                                     308     2                                                                     338     5                                                                     340     16                                                                    350     8                                                                     393     18                                             28     42.6  --   55.9 290     85                                                                    306     50                                                                    325     47                                                                    334     49                                                                    348     52                                                                    365     50                                             29     47.9  22.3 29.8 282     55                                                                    321     49                                                                    349     45                                                                    368     43                                                                    387     43                                                                    406     47                                             __________________________________________________________________________

EXAMPLES 30-31

2.4- and 2,6-DMA were equilibrated by reacting them with 2,4,6-TMA overHY zeolite catalyst using a procedure similar to that used for Examples27-29. The results are summarized in Table IV.

EXAMPLES 32-34

Equilibration of 2,3-, 2,5-, and 3,4-DMA by reacting each withm-toluidine over the HY zeolite catalyst was carried out using aprocedure similar to that described for Examples 27-29. The results aregiven in Table V. The product can also contain some aniline, o- andp-toluidine, and 2,4- and 2,6-DMA.

EXAMPLES 35-39

Equilibration of toluidines in the presence of HY zeolite was carriedout in a manner similar to that used for Examples 27-29: 3 g of HYzeolite were used, the feed solution flow rate was 3 ml/hr in each caseand the nitrogen flow rate was 10 ml/min. Results are summarized inTable VI. As can be seen from Example 35, the ortho and para isomers arenearly completely equilibrated before any appreciable amount of metabegins to form. Examples 37, 38 and 39 show the role played by anilinewhen HY catalyst is used as well as the importance of thedisproportionation of toluidines to DMA's and aniline (Example 39). Onthe basis of beginning with p-toluidine/aniline and m-toluidine/anilinefeeds, the three component equilibrium is approached as shown in FIG. 1.While a 10% solution of ortho-toluidine in aniline approaches the curveshown, a 1:1 mix of aniline and o-toluidine does not follow the curve,but bends toward the three component equilibrium much earlier. Pureo-toluidine proceeds almost straight to the three component equilibrium.

                                      TABLE IV                                    __________________________________________________________________________                                   Product                                                Feed Composition (mole %)                                                                     Reaction Temp                                                                         ##STR7##                                      Example No.                                                                          2,4,6-TMA                                                                           2,4-DMA                                                                            2,6-DMA                                                                            (degrees)                                                                             (mole percent)                                 __________________________________________________________________________    30     48    --   52   252     96                                                                    273     95                                                                    310     79                                                                    340     38                                                                    363     37                                                                    405     40                                                                    435     46                                                                    471     51                                                                    502     68                                             31     44    56   --   290      7                                                                    318     19                                                                    355     28                                                                    387     33                                                                    423     27                                                                    467     30                                                                    501     25                                             __________________________________________________________________________

                                      TABLE V                                     __________________________________________________________________________    Feed Composition                                                              Example                                                                            m-toluidine                                                                         DMA      Reaction                                                                           Product Composition (mole %)                         No.  (mole %)                                                                            (isomer/mole %)                                                                        Temp °                                                                      m-toluidine                                                                         2,3-DMA                                                                            3,4-DMA                                                                            2,5-DMA                              __________________________________________________________________________    32   53    2,3-DMA/46                                                                             293  53    46   --   --                                                       322  54    40   2.0  1.3                                                      346  57    35   2.8  2.4                                                      382  58    31   3.8  4.1                                                      420  56    21   4.8  7.4                                  33   52    3,4-DMA/44                                                                             282  61    --   39   --                                                       341  64    0.7  31   3.3                                                      371  64    1.3  27   6.4                                                      405  65    2.2  24   8.0                                                      438  62    5.3  16   11                                                       460  55    6.9  10   11                                                       483  50    7.8  8.8  9.4                                                      508  48    6.0  12   7.2                                  34   53    2,5-DMA/45                                                                             302  54    0.8  --   44                                                       320  57    1.1  4.7  36                                                       340  57    1.2  4.8  35                                                       363  57    4.6  4.9  31                                                       391  58    3.5  5.7  27                                                       403  56    5.2  6.3  23                                                       423  50    6.5  5.5  16                                                       453  45    6.9  4.8  14                                                       473  44    5.9  3.9  13                                   __________________________________________________________________________

                                      TABLE VI                                    __________________________________________________________________________    Feed                                                                          Example                                                                            Composition                                                                           Reaction                                                                           Product Composition (mole %)                                No.  (mole ratio)                                                                          Temp °                                                                      Aniline                                                                            o-toluidine                                                                         p-toluidine                                                                         m-toluidine                                                                         2,6-DMA                                                                            2,4-DMA                                                                            2,4,6-TMA                  __________________________________________________________________________    35   0.3 o-toluidine:                                                                      375  63   18    13    1.1   1.1  3.6  6.4                             0.7 p-toluidine:                                                                      397  54   18    16    1.0   1.6  --   --                              1 aniline                                                                             440  63   18    11    3.5   1.0  3.1  0.6                                     447  68   17    11    4.3   2.6  6.6  --                                      462  64   16    11    5.5   2.3  0.8  0.1                                     480  67   15    9.6   8.3   --   --   --                                      500  70   12    6.0   9.2   0.3  0.9  0.7                        36   1 m-toluidine:                                                                        290  52   --    --    46    --   1.4  0.2                             1 aniline                                                                             320  53   --    0.1   46    --   0.4  0.1                                     354  53   0.3   0.3   46    --   0.3  0.2                                     407  52   0.9   0.8   46    --   0.5  0.3                                     454  54   3.0   2.1   39    --   0.9  0.5                                     500  59   5.3   3.6   30    0.3  0.9  0.6                        37   1-o-toluidine:                                                                        375  56   30    6.7   1.0   1.1  3.8  0.4                             1 aniline                                                                             392  56   29    6.6   1.3   1.1  3.4  0.3                                     409  56   30    6.1   1.8   1.1  3.5  --                                      437  59   27    5.5   3.7   0.7  2.4  0.3                                     453  60   26    5.2   5.0   0.6  1.7  0.4                                     473  63   24    4.8   6.5   --   0.8  --                         38   .11-o-toluidine:                                                                      317  88   11    --    --    --   --   --                              .89 aniline                                                                           357  88   9.3   1.5   0.2   0.1  0.1  0.2                                     402  88   7.1   2.9   0.5   0.2  0.2  0.3                                     415  90   9.1   0.7   0.2   --   --   --                                      423  90   6.9   2.4   0.5   --   --   0.5                                     444  90   6.2   2.2   0.8   --   --   0.4                                     451  90   6.9   1.4   0.8   --   --   0.3                                     468  91   5.3   1.8   1.3   --   --   0.3                                     489  92   3.9   1.3   1.8   --   --   --                         39   o-toluidine                                                                           370  21   59    --    --    3.1  16   1.0                                     388  20   57    4.6   1.0   3.0  13   0.6                                     403  24   56    --    --    3.4  15   1.3                                     422  18   60    2.6   2.2   2.3  10   0.9                                     441  13   76    1.6   3.1   1.9  6.6  0.7                                     469  20   52    3.7   5.8   2.4  6.8  1.5                                     492  24   53    4.8   8.2   2.5  6.0  2.0                        __________________________________________________________________________

EXAMPLE 40-48

Equilibration of toluidines in the presence of other catalysts wasconducted by using a procedure similar to that used for Examples 27-29:3 g of catalyst were used, the feed solution flow rate was 2.2 ml/hr andthe nitrogen flow rate was 10 ml/min. Results are shown in Table VII.

EXAMPLES 49-50

Equilibration of ethylanilines in the presence of HY zeolite wasconducted by using a procedure similar to that used in Examples 27-29. Asolution of aniline and either p-ethylaniline or o-ethylaniline waspassed over 3 g of HY zeolite catalyst at atmospheric pressure and agiven reaction temperature at a flow rate of 2.2 ml/hr with a nitrogengas flow rate of 10 ml/min. The relative amounts of aniline andethylanilines in the product are shown in Table VIII. There was also asmall fraction of high-boiling unidentified material in the product.

                                      TABLE VII                                   __________________________________________________________________________              Feed   Reaction                                                     Ex.       Composition                                                                          Temp  Product Composition (mole %)                           No. Catalyst                                                                            (mole ratio)                                                                         (degrees)                                                                           Aniline                                                                             o-toluidine                                                                         p-toluidine                                                                         m-toluidine                                                                         2,6-DMA                                                                            2,4-DMA                                                                            2,4,6-TMA            __________________________________________________________________________    40  (1)   1 p-toluidine:                                                                       300   75    12    8.0   2.4   0.4  0.3  0.7                            1 aniline                                                           41  (2)   1 p-toluidine:                                                                       375   56    --    43    --    0.5  --   --                             1 aniline                                                                            500   68    6.0   22    1.0   2.0  --   --                   42  (3)   1 p-toluidine:                                                                       375   54    --    46    --    --   --                                  1 aniline                                                                            500   66    4.3   26    0.3   2.4  --                        43  (4)   1 p-toluidine:                                                                       400   54    --    46    --    --   --   --                             1 aniline                                                                            500   65    2.9   29    --    2.2  --   --                   44  (5)   1 p-toluidine:                                                                       375   64    4.3   29    3.5   --   --                                  1 aniline                                                                            500   51    --    49    --    0.5  --                        45  (6)   1 p-toluidine:                                                                       375   57    0.6   41    --    1.1  --   --                             1 aniline                                                                            500   65    1.5   32    0.6   0.9  --   --                   46  (7)   1 o-toluidine:                                                                       500   73    24    1.7   0.7   0.4  0.5  --                             2 aniline                                                                            500   79    18    1.6   0.6   0.2  0.4  --                   47  (8)   1 o-toluidine:                                                                       500   77    19    0.9   1.7   0.2  0.2  --                             2 aniline                                                           48  (9)   1 o-toluidine:                                                                       500   82    15    1.0   0.9   --   --   --                             2 aniline                                                           __________________________________________________________________________     (1) HY                                                                        (2) 91% Al.sub.2 O.sub.3 /6% SiO.sub.2 (amorphous)                            (3) 99% Al.sub.2 O.sub.3                                                      (4) 99% Al.sub.2 O.sub.3                                                      (5) 87% SiO.sub.2 /13% Al.sub.2 O.sub.3                                       (6) 10% MoO.sub.3 /Al.sub.2 O.sub.3                                           (7) 33% Cr.sub.2 O.sub.3 /Al.sub.2 O.sub.3                                    (8) 10% MoO.sub.3 /Al.sub.2 O.sub.3                                           (9) 10% V.sub.2 O.sub.5 /SiO.sub.2 - containing Al.sub.2 O.sub.3         

                                      TABLE VIII                                  __________________________________________________________________________         Feed     Reaction                                                                           Product Composition (mole %)                               Example                                                                            Composition                                                                            Temp      o-ethyl-                                                                           p-theyl-                                                                           m-ethyl-                                    No.  (mole ratio)                                                                           (degrees)                                                                          Aniline                                                                            aniline                                                                            aniline                                                                            aniline                                     __________________________________________________________________________    49   1 p-ethyl-aniline:                                                                     300  55   4.0  41   --                                               1 aniline                                                                              330  58   10   32   --                                                        360  60   15   25   --                                                        390  66   13   16   4.4                                                       420  76   6.6  6.9  10                                          50   1 o-ethyl-aniline:                                                                     275  46   53   0.6  --                                               1 aniline                                                                              300  49   49   1.9  --                                                        330  53   39   7.5  --                                                        360  58   28   12   2.5                                                       390  60   24   14   2.4                                                       420  58   16   11   5.3                                         __________________________________________________________________________

The invention being claimed is:
 1. A process for interconverting2,3-dimethylaniline, 2,5-dimethylaniline, and 3,4-dimethylaniline bytransalkylation with m-toluidine, comprising contacting a mixturecomprising one or more of 2,3-dimethylaniline, 2,5-dimethylaniline, and3,4-dimethylaniline with m-toluidine in the presence of a stronglyacidic alumina-silica catalyst at a temperature of from about 250° toabout 525° C. and at a pressure of from about 10 kPa to about 10 MPa,with the proviso that where the catalyst is a zeolite it has poredimensions of at least about 0.52 nm and has cages with dimensionsgreater than about 0.75 nm.
 2. A process according to claim 1, conductedat a temperature from about 300° C. to about 500° C.
 3. A processaccording to claim 2, wherein the catalyst is a type X or type Yzeolite.
 4. A process according to claim 3, wherein the catalyst is ahydrogen-exchanged type Y zeolite.